Method and apparatus for strain relieving surface mount attached connectors

ABSTRACT

An interconnect structure that includes a component circuit board containing a plurality of electrical components, and a wafer connector assembly. The wafer connector assembly includes a plurality of interconnect circuit boards that are in electrical connection with the components circuit board through a plurality of rows of solder joints, the plurality of interconnect circuit boards having a connection end including at least one contact. An adhesive is present structurally reinforcing at least a row of the solder joints that is proximate to the connection end of the plurality of interconnect circuit boards of the wafer assembly.

BACKGROUND Technical Field

The present disclosure relates to the strain relief of solder jointsbetween connectors and printed circuit boards.

Description of the Related Art

A design practice in electrical interconnection is strain relief.Movement or disturbance to an electrical connection can causeintermittent faults (open circuits) or catastrophic failure. Typically,separable connectors rely on plastic latches or locking parts that areintegrated with plastic housings which attempt to provide controlledlocation and alignment of contacts. In these examples, as well asothers, contact points can be sensitive to movement from mechanicaldisturbances caused by handling, vibration and shock.

SUMMARY

In one aspect, an interconnect to a circuit board is provided thatincludes an adhesive enhancement to a zone of the interconnect includingsolder joints that can be vulnerable to damage, e.g., by insertionforce, handling, vibration and shock. In some embodiments, theinterconnect to the circuit board includes a component circuit boardcontaining a plurality of electrical components and a wafer connectorassembly. The wafer connector assembly includes a plurality ofinterconnect circuit boards that are in electrical connection with thecomponents circuit board through a plurality of rows of solder joints.The plurality of interconnect circuit boards include a connection endhaving at least one contact and a back end that is opposite theconnection end. An adhesive is represent encapsulating at least a row ofsolder joints from said plurality of rows of solder joints that isproximate to the connection end of the plurality of interconnect circuitboards of the wafer assembly.

In another aspect, an interconnect system is provided. In someembodiments, the interconnect system includes a mid plane board forintegration with a computing system the mid plane board including aheader connection site; and a component circuit board for electricalengagement to the mid plane board by reversible electrical connection tothe header connection site through a wafer connector assembly that issolder joint connected to the component circuit board. The waferconnector assembly includes a plurality of interconnect circuit boardsthat are in electrical connection with the components circuit boardthrough a plurality of rows of solder joints. The plurality ofinterconnect circuit boards include a connection end having at least onecontact and a back end that is opposite the connection end. An adhesiveis represent encapsulating at least a row of solder joints from saidplurality of rows of solder joints that is proximate to the connectionend of the plurality of interconnect circuit boards of the waferassembly.

In another aspect of the present disclosure, a method of forming aninterconnect for a component circuit board is provided that includes anadhesive enhancement to a zone of the interconnect including solderjoints that can be vulnerable to damage, e.g., by insertion force,handling, vibration and shock. In some embodiments, the method mayinclude providing a component circuit board containing a plurality ofelectrical components. A wafer connector assembly including a pluralityof interconnect circuit boards is then connected to the componentcircuit board with a plurality of rows of solder joints, wherein theplurality of circuit boards are in electrical communication with atleast one of the components in the component circuit board through thesolder joints, and the plurality of interconnect circuit boards includea connection end having at least one contact and a back end that isopposite the connection end. Encapsulating with an adhesive at least onerow of solder joints from said plurality of rows of solder joints thatis proximate to the connection end of the plurality of interconnectcircuit boards of the wafer assembly.

BRIEF DESCRIPTION OF DRAWINGS

The following detailed description, given by way of example and notintended to limit the disclosure solely thereto, will best beappreciated in conjunction with the accompanying drawings, wherein likereference numerals denote like elements and parts, in which:

FIG. 1A is a front perspective view of a computing system includingmultiple blade server boards that plug into a mid plane board via matingmale and female surface mount connectors that are attached to the midplane board and blade server board assemblies respectively, inaccordance with some embodiments of the present disclosure.

FIG. 1B is a perspective view of component circuit board, i.e., bladeserver board, in accordance with some embodiments of the presentdisclosure.

FIG. 2 is a perspective view of a single blade server board plugginginto, i.e., making a reversible electrical connection to, a mid planeboard, in accordance with some embodiments of the present disclosure.

FIG. 3 is a perspective view of the wafer connector assembly inelectrical communication to the component circuit board through solderjoints, in which the wafer connector assembly is being inserted into theheader site of a mid plane board, wherein the pluggable connection isorthogonal to the plane of the solder joints, in accordance with oneembodiment of the present disclosure.

FIG. 4A is a front perspective view of a wafer connector assembly solderjoint connected to a component circuit board depicting the connectionend of the circuit boards in the wafer connector assembly, wherein thesolder joints are fully encapsulated in a reinforcing adhesive, inaccordance with one embodiment of the present disclosure.

FIG. 4B is a side perspective view of the wafer connector assemblydepicted in FIG. 4A.

FIG. 4C is a side perspective view of another embodiment of the waferconnector assembly including an adhesive reinforcement to only the firstrows of solder joints that are proximate to the connection end of theplurality of interconnect circuit boards of the wafer connectorassembly.

FIG. 4D is a side perspective view of another embodiment of the waferconnector assembly including an adhesive reinforcement to the first rowsof solder joints that are proximate to the connection end of theplurality of interconnect circuit boards of the wafer connector assemblyand the back rows of solder joints that are proximate to the backsideend of the plurality of interconnect circuit boards of the waferconnector assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments is intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the methods and structures of the present disclosure. Forpurposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the embodiments of the disclosure,as it is oriented in the drawing figures. The terms “positioned on”means that a first element, such as a first structure, is present on asecond element, such as a second structure, wherein interveningelements, such as an interface structure, e.g. interface layer, may bepresent between the first element and the second element. The term“direct contact” means that a first element, such as a first structure,and a second element, such as a second structure, are connected withoutany intermediary conducting, insulating or semiconductor layers at theinterface of the two elements.

Strain relief is a design practice in separable electricalinterconnection to prevent mechanical loading to an electricalconnection. However, it has been determined that strain relief hastypically not been practiced with solder joints, because of the inherentstrength of solder and low loads from handling, shock and vibration. Inthe case of solder interconnection, strict adherence to strain reliefdesign is not followed for several reasons. Unlike a separable connectorsystem, in some examples a solder joint is a strong, continuousmetallurgical structure and not susceptible to micro-motion at aninterface. Further, there is typically a high number of solder jointsper component unit mass and thus, any impact shock loading is much lessthan the yield and fracture strength of the solder joints.

However, for high end computers and servers, such as those disclosedherein, e.g., depicted in FIG. 1A, the number of input/outputconnections is much higher (>100×) than a typical feature option cardfor low end personal computers (PC), and mid-range servers andworkstations. It has been determined, that in these instances, theinsertion forces become significant and cannot be accomplished manually,but require mechanical assistance. An example is a connector design thatrequires simultaneous mating of more than 5000 blade to springconnections. The insertion forces are nominally about 55 kg which anarray of an equal number of solder joint must withstand. In someexamples, the connector designs require an insertion plane P1 that isorthogonal to the solder joint plane P2, as depicted in FIGS. 2 and 3.The solder joint plane P2 is along the direction of the height of thesolder joints 30, which extends from the connection to the componentcircuit board 10 to the wafer connection assembly 20 (also referred toas ventura connector). In this case, high insertion forces (F_(i)) arepreferentially transmitted to a front row or rows of solder joints andimpart a peel (F_(pb-shear)) or tensile force (F_(pb-tension)).Additionally, the mechanism for insertion guidance can have a long leverarm and therefore, impart loading moments, i.e., F_(top) and F_(side).Solder joints 30 have been damaged in such a design, resulting inelectrical opens and in cracks that are incipient in nature andrepresent latent or field reliability failures.

These methods and structures that are disclosed herein in someembodiments can provide strain relief to surface mount solder attachedconnectors. For example, the methods and structures that are disclosedherein can provide strain relief to surface mount solder attachedconnectors that experience high insertion forces with tensile or peelcomponents, or insertion forces that damage solder joints, which canresult in immediate or latent opens. As will be described in furtherdetail below, a polymeric, liquid adhesive is introduced into thepopulation of solder joints and cured. The cured properties of theadhesive allow uniform distribution of insertion forces over the entireadhesive bond area, rather than high, concentrated forces over a lowpercent of the total solder joint population. Repeated connector matingsare possible as required for electrical testing, trouble shooting,repair and upgrade while maintaining reliable solder joint integrity.The methods and structures of the present disclosure are now describedin further detail with reference to FIGS. 1A-4D.

In some embodiments, an interconnect system is provided that includes aheader site 35 for integration with a computing system chassis 40; and acomponent circuit board 10 for reversible electrical connection to theheader connection site 35 of the computing system chassis 40 through awafer connector assembly 20 that is connected through solder joints 30to the component circuit board 10, as depicted in FIGS. 1A and 2.

Referring to FIG. 2, the component circuit board 10 may be a printedcircuit board and may include a number of electrical components 11integrated therewith, such as memory, resistors, capacitors, lightemitting diodes (LEDs), transistors, inductors, integrated circuits, andcombinations thereof. Transistors integrated into the component circuitboard may include field effect transistors and fin type field effecttransistors. In some embodiments, the component circuit board 10 may bea blade server board.

As will be described below, the wafer connector assembly 20 includes aplurality of interconnect circuit boards 21 that are in electricalconnection with the components circuit board 10 through a plurality ofrows of solder joints 30, as depicted in FIGS. 3-4D. The integratedcircuit boards may be laminated printed circuit boards (PCBs). In someembodiments, each of the interconnect circuit boards 21 may include atleast one pin receptacle 22 (typically a plurality of pins) for engagingthe pins from the header connection site 35 of the computer system 100.The pins receptacle 22 may include a conductive component, such ascopper, for reversibly engaging the pins of the header connection site35. The pins receptacle 21 may be configured for engagement to the pinsat the header connection site 35. The end of the plurality ofinterconnect circuit boards 21 of the wafer connector assembly 20 thatincludes the pins 22 may be referred to as the connection end S1 of theplurality of interconnect boards 21. The end of the plurality ofinterconnect circuit boards 21 of the wafer connector assembly 20 thatis opposite the connection end S1 may be referred to as the back sideend S2 of the wafer connector assembly 20. The wafer connector assembly20 may also include framing 23 for providing some mechanical support forthe wafer connector assembly, wherein the framing may include guidingmembers, such as guide openings for receiving guide pins. Although FIGS.3-4D depict a wafer connector assembly 20 including 13 interconnectcircuit boards 21, the present disclosure is not limited to only thisexample, as any number of interconnect circuit boards 21 may be includedin the wafer connector assembly 20.

A plurality of solder joints 30 provide for electrical communicationbetween the circuits on the printed circuit boards of the plurality ofinterconnect circuit boards of the wafer connector assembly 20 and thecircuits on the component circuit board 10. The plurality of solderjoints also provide for physical engagement of the wafer connectorassembly 20 to the component circuit board. The term “solder”, as usedherein, refers to any metal or metallic compound or alloy that is meltedand then allowed to cool in order to join two or more metallic surfacestogether. The plurality of solder joints 30 may be composed of a metalsuitable for soldering. For example, in some embodiments, the solderjoints 30 may be composed of a eutectic alloy of tin and lead or a leadfree solder composition. In some embodiments, the solder joints having aheight ranging from 0.5 mm to 3 mm. In other examples, the solder joints30 have a height greater than 1 mm. In some embodiments, the array ofsolder joints may have a total area greater than 30 mm×200 mm.

An adhesive 45 is present encapsulating 45, 45 a, 45 b at least a row ofsolder joints 30 to structurally reinforce the plurality of rows ofsolder joints 30, as depicted in FIGS. 4A-4D. The adhesive 45 may bepolymeric. In some embodiments, the adhesive 45 can be epoxy basedresin. In some examples, the adhesive 45 can be epoxy resin with filler,epoxy acrylate with filler, or polymer with proper filler. The adhesive45 is non-conductive. In some examples, epoxy resin formulations thatmay be suitable for the adhesive 45 can include, for example, highpurity diglycidyl ether of bisphenol F or diglycidyl ether of bisphenolA along with high performance or multifunctional resins, such as thediglycidyl ether of naphthalene diol or the triepoxide ofpara-aminophenol. It is noted that this is only one example of an epoxycomposition that may be used as the adhesive 45 of the presentdisclosure. Other adhesive compositions, and other epoxy based resins,are equally suitable for the adhesive 45 that structurally reinforcesthe plurality of rows of solder joints 30. Further details regarding theadhesive compositions are provided below.

FIGS. 4A and 4B depict one embodiment of the present disclosure in whichthe solder joints 30 are fully encapsulated in a reinforcing adhesive.By “fully encapsulated” it is meant that each solder joint 30 for everyrow of solder joints 30 is surrounded by an adhesive so that no point ofthe solder joint 30 is exposed. FIG. 4C depicts another embodiment ofthe wafer connector assembly 20 including an adhesive reinforcement 45 ato only the first row of solder joints 30 that are proximate to theconnection end S1 of the plurality of interconnect circuit boards 21 ofthe wafer connector assembly 20. In this embodiment, each of the solderjoints 30 in the first row are encapsulated in the adhesive 45 a, i.e.,entirely encapsulated, but the remainder of solder joints 30 that arenot in the first row and not in contact with adhesive and are exposed.FIG. 4D depicts another embodiment of the wafer connector assembly 20including an adhesive reinforcement 45 a, 45 b to the first rows ofsolder joints 30 that are proximate to the connection end S1 of theplurality of interconnect circuit boards 21 of the wafer connectorassembly 20 and the back row of solder joints 30 that are proximate tothe backside end S2 of the plurality of interconnect circuit boards ofthe wafer connector assembly.

FIG. 1A depicts one embodiment of a computing system 100 as employed inthe present disclosure including multiple blade server boards, which maybe referred to as one example of a component circuit board 10, in whichthe blade server boards plug into a mid plane board 36. The mid planeboard 36 includes the header connection site 35 and provides forengagement to the computer system chassis 40. The mid plane board 36provides for power and signal to be transmitted to each of the componentcircuit boards 10 that are engaged thereto. In some embodiments,reversible electrical connection, i.e., the ability to connect anddisconnect, between the header connection site 35 of the mid plane board36 and the component circuit board 10, e.g., blade server board, may beprovided by mating male and female surface mount connectors that areattached to the mid plane board and blade server board assembliesrespectively. As will be discussed below, the component circuit board 10includes a solder joint 30 mounted wafer connector assembly 20 forengaging the header connection site 35 of the mid plane board 36.

FIG. 1B depicts one embodiment of a blade server board that may providethe component circuit board 10, in accordance with the presentdisclosure. The typical dimensions of a blade board assembly may includea width W1 of approximately 150 mm, a height H1 of approximately 380 mm,and a depth D1 of approximately 790 mm.

Referring to FIGS. 1A and 1B, in some embodiments, mechanical handlingequipment called node actuation mechanism (NAM) 37 is required to alignand plug the large and heavy node-assembly, typically weighing about 70kg, into the mid plane 36. In some embodiments, the tight spacing of theadjacent component circuit boards 10, e.g., blade assemblies, is areason for the use of the NAM 37 for controlled insertion and removal ofthe blades, i.e., component circuit boards 10. As can be seen in FIG.1A, the component circuit boards 10, e.g., blade server boards, can mateto top and bottom positions on the mid plane 36. In some embodiments,every component circuit board 10, e.g., blade server board, has a bankof connectors, e.g., that are surface mount soldered to it via an arrayof several thousand solder joints. Similarly, every mating position forevery blade on the mid plane has a bank of connectors, called headers,which may be collectively referred to as a wafer connector assembly 20,that are surface mount soldered to the component circuit board 10 via anarray of several thousand solder joints 30. The component circuit board10 interconnects with the mid plane 36 position via separable pin andspring contacts that are housed in the surface mount connectors, i.e.,wafer connector assembly 20.

It is noted that although FIG. 1A depicts eight component circuit boards10 being engaged to a single mid plane board 36, the present disclosureis not limited to only this example, as any number of component circuitboards, as well as mid plane boards 36, may be integrated into acomputer system chassis 40.

FIG. 2 shows a schematic of a component circuit board 10 being insertedto a bottom position on the mid plane board 36. In some embodiments,pins 38 extend vertically downward from the surface mount connector,i.e., header connection site 35, on the mid plane 36 and engage withfemale spring contacts that are housed in the surface mount connector,i.e., wafer connector assembly 20, of the blade assembly. In someembodiments, during assembly, because of the several thousand pin tospring matings required per component circuit board 10, e.g., bladeserver board, to the header connection site 35, e.g., to the mid planeboard 25, forces on the order of 55 kg may be required to engage thecomponent circuit board 10 to the header connection site 35.

Referring to FIGS. 3-4D, the solder joints 30 of the connector, i.e.,wafer connector assembly 20, on the component circuit board 10, e.g.,blade server board assembly, can experience non-uniform loading. FIG. 3is a schematic side view illustrating a wafer connector assembly 20soldered to a component circuit board 10, in which the pluggableconnection to the header connection site 35 of the computer systemchassis is in a direction orthogonal to the plane of solder joints 30.In some embodiments, the non-uniform loading experienced by the solderjoints 30 that connect the wafer connector assembly 20 to the componentcircuit board 10 include tensile F_(pb-tension) and peel componentsF_(pb-shear) concentrated on the row of solder joints 30 a closest tothe mating pins to spring contacts of the wafer connector assembly 20,as shown in FIG. 3.

FIG. 4A shows a front view of the wafer connector assembly 20 and pinreceptors 22, e.g., female spring contacts, for receiving the pins 38from the header connection site 35. FIG. 4B is a view of the structuredepicted in FIG. 4A rotated 90° into the page to depict a side view ofthe wafer connector assembly 20. The arrow identified by referencenumber F_(i) is the insertion forces experienced by the wafer connectorassembly 20, as the wafer connector assembly 20 is engaged to the headerconnection site 35. The arrow identified by reference number F_(rt) isthe reaction tensile force on the leading row of solder joints 35 a inresponse to the insertion forces F_(i). The arrow identified F_(c) isthe reaction compression force, which is a compressive force that isinduced on the final row of solder joints 35 b, in response to theinsertion forces F_(i).

Referring to FIG. 4B, from the side view, the leading row of solderjoints 30 a are visible, which are most vulnerable to damage duringconnector mating, i.e., engagement of the wafer connector assembly 20into the header connector site 35 of the mid plane board 36. The nextrow behind the leading row is also susceptible to damage but to a lesserdegree and so forth. The first few rows of solder joints 30 may becollectively referred to as the zone vulnerable to damage 50.

In order to provide a robust strain relief system for all solder joints,the adhesive material 45 a is introduced to a minimum the first row ofsolder joints 30 a, and in some examples the entirety of the zonevulnerable to damage 50, as depicted in FIG. 4C. By introducing theadhesive material 45 a to the first row of solder joints 30 a, theadhesive counteracts the reaction tensile force F_(rt) that is inducedon the front row of solder joints 30 a and the zone vulnerable to damage50 by the insertion forces experienced by the wafer connector assembly20 when being engaged to the header connection site 35.

Referring to FIG. 4D, in some embodiments, the adhesive 45 a, 45 b isapplied to the first row of solder joints 30 a and the last row ofsolder joints 30 b. By introducing the adhesive material 45 a to thefirst row of solder joints 30 a, the adhesive counteracts the reactiontensile force F_(A) that is induced on the front row of solder joints 30a and the zone vulnerable to damage 50 by the insertion forcesexperienced by the wafer connector assembly 20 when being engaged to theheader connection site 35. By introducing the adhesive material 45 b tothe last row of solder joints 30 b, the adhesive counteracts thereaction compressive force F_(c) that is induced on the last row ofsolder joints 30 b by the insertion forces experienced by the waferconnector assembly 20 when being engaged to the header connection site35.

FIGS. 4A and 4B depict one embodiment of a wafer connector assemblysolder joint 20 wherein all the solder joints 30 are fully encapsulatedin a reinforcing adhesive 45. This means that in addition to the frontrow and final row 30 a, 30 b being encased with adhesive, all the rowsof solder joints between the first and final rows 30 a, 30 b are alsoencased in their entirety.

In another aspect of the present disclosure, a method of forming aninterconnect for a component circuit board is provided that includesproviding a component circuit board containing 10 a plurality ofelectrical components 11; and electrically connecting a wafer connectorassembly 20 including a plurality of interconnect circuit boards 22 tothe component circuit board 10 with a plurality of rows of solder joints30. The plurality of circuit boards 10 are in electrical communicationwith at least one of the components 11 in the component circuit board 10through the solder joints 30. The method may further includeencapsulating with an adhesive 45, 45 a, 45 b at least one row of solderjoints 30, 30 a, 30 b from said plurality of rows of solder joints thatis proximate to the connection end S1 of the plurality of interconnectcircuit boards of the wafer connection assembly 20. The adhesive 45, 45a, 45 b reduces strain in the solder joints 30 when the connection endS1 having at least one contact is engaged into a header site 35 ofcomputer chassis 40. In some embodiments, the adhesive 45 a, 45 b, 45composition is selected as a ball grid array (BGA) like underfill tofill the gap between the wafer connector assembly 20 (also referred toas ventura connector) and the component circuit board 10, e.g., bladeserver board, to provide mechanical integrity to the solder joints 30.The methods disclosed herein can provide a void-free gap fill forencapsulating at least one of the solder joints 30, and in someinstances all of the solder joints 30. In some embodiments, thecomposition of the adhesive 45, 45 a, 45 b is selected to provide anadhesive material with glass transition temperature (Tg) of 75° C., CTE1and CTE2 (coefficient of thermal expansion) of 70 and 210 ppm/° C. belowand above Tg, respectively, viscosity of 3 Pa*s (or equivalent materialwith acceptable flow characteristics). In another embodiment, thecomposition of the adhesive 45 to provide an adhesive material with a Tgof 125 C, CTE1 of 31 ppm/° C., and a storage modulus of 4 GPa.

In some embodiments, the apparatus for dispensing the adhesive 45 a, 45b may include at least a reservoir for containing adhesive 45 a, 45 b, apumping mechanism for moving the adhesive 45 a, 45 b, 45 c from thereservoir, a connecting tube for transmitting the pumped adhesive to adispensing needle, and a dispensing needle for dispensing the adhesive45 a, 45 b, 45 c to the solder joints 30. In some embodiments, theadhesive 45 a, 45 b, 45 c is injected under pressure from the dispensingneedle uniformly within the space between the solder joints 30, 30 a, 30b as well as surrounding the solder joints 30 that are present at theperimeter positions of the array of solder joints. In some embodiments,the apparatus for dispensing the adhesive 45 a, 45 b, 45 c includes amounting table for supporting the component circuit board 10 whileapplying the adhesive 45 a, 45 b, 45 c to the rows of solder joints 30,30 a, 30 b. In some embodiments, the mounting table 30 may be adjustableto change the angle of the component circuit board 10 to affect the flowof adhesive through the plurality of rows of solder joints 30, 30 a, 30b during the application of the adhesive 45 a, 45 b, 45 c. For example,the mounting table may tilt to modulate the component circuit board 10up to 15 degrees from horizontal during the application of the adhesive45, 45 a, 45 b. In other examples, the mounting table may tilt tomodulate the component circuit board 10 up to 10 degrees from horizontalduring the application of the adhesive 45, 45 a, 45 b.

In some embodiments, the adhesive 45 a, 45 b, 45 c is dispensed at atemperature of 54° C.+/−5° C. with a dispensing needle that has aninside diameter between 0.4 mm to 0.6 mm, using multiple dispensepasses. In some embodiments, because the height of the solder joints islarge, e.g., greater than 1 mm, as are the x and y dimensions of thetotal area (>30×200 mm), gravity may be used to facilitate theintroduction of the adhesive 45 to the rows and between the rows andcolumns of solder joints 30. The component circuit board 10 is held at a10 degree angle α from horizontal to assist in the dispense/flow, asdepicted in FIGS. 4A-4C.

In some embodiments, heating the component circuit board 10, to whichthe wafer connector assembly 20 is attached through the solder joints30, also facilitates movement of the adhesive 45, 45 a, 45 b by allowinga reduction in viscosity. Heating of the component circuit board 10and/or the wafer connector assembly 20 can be done by a hot plate, orenhanced tooling, which involves a heating block with several heaters inthe block, to ensure that there is not a large temperature gradientacross the length of the component circuit board 10 and/or the waferconnector assembly 20.

Depending on the viscosity of the adhesive 45 a, 45 b, 45 c, the effectfrom gravity is controlled by adjusting the angle α from a horizontalposition of a process platform that supports the component circuit board10. In some embodiments, vision cameras are positioned at the exit sideof the row of solder joints 30 that is opposite from the feed side (atwhich the dispensing needle injects adhesive 45, 45 a, 45 b) and providea visual monitor for the appearance of the adhesive 45 a, 45 b, 45 c.When the adhesive 45 a, 45 b, 45 c reaches the exit side of the rows ofsolder joints 30 a, 30 b, the adjustable platform is quickly returned toa horizontal position, i.e., angle of 0 degrees, to prevent the adhesive45 a, 45 b, 45 c from spilling out.

Complete adhesive 45 a, 45 b, 45 c introduction around the solder joints30 of the connector, i.e., wafer connector assembly 20, in both x/y andz requires about 45 passes and approximately 30 g of adhesive 45 a, 45b, 45 c. The material is dispensed until it is seen on the exit side ofthe connector (by eye, or with a camera/vision system). Using enhancedtooling, all three sections of the connector can be dispensedsimultaneously using three syringes, i.e., needle dispensers to decreasecycle time.

After application of the adhesive 45 a, 45 b, 45 c, the componentcircuit board 10 is adjusted to horizontal (zero degrees), and theadhesive material 45 a, 45 b, 45 c is cured in-situ using shroud heaterspositioned above the wafer connector assembly 20. Cure temperature andtime may be on the order of approximately 110° C. for 10 minutes.Alternatively, curing can be accomplished by placing the componentcircuit board 10 including the wafer connector assembly 20 in a box ovenor inline furnace and using an appropriate ramp and dwell.

As noted above, in some embodiments, requiring complete encapsulation ofthe solder joints 30, as depicted in FIGS. 4A and 4B, complete adhesive45 a, 45 b, 45 c introduction around the solder joints 30 of theconnector, i.e., wafer connector assembly 20, in both x/y and z requiresabout 45 passes and approximately 30 g of adhesive 45 a, 45 b, 45 c.Rather than complete reinforcement of the array of solder joints, asdepicted in FIGS. 4A and 4B, partial reinforcement, as depicted in FIGS.4C and 4D, offers the advantage of less process time and less material.Partial reinforcement can be achieved by using a higher viscosityadhesive, such as Namics 1883-2. The adhesive 45 a, 45 b is dispensedeither into the A row space (identified by “A”) only, as depicted inFIG. 4C, or only into the A row space (identified by “A”) and P rowspace (identified by “P”), as depicted in FIG. 4D.

In some embodiments, the adhesive 45, 45 a, 45 b is filling spacebetween adjacent rows of solder joints 30 having a Z gap ofapproximately 1 mm to 2 mm in height, and a width of approximately 30 mmto 35 mm (e.g., 33 mm) and a length dimension on the order of 250 mm(10″).

While the methods and structures of the present disclosure have beenparticularly shown and described with respect to preferred embodimentsthereof, it will be understood by those skilled in the art that theforegoing and other changes in forms and details may be made withoutdeparting from the spirit and scope of the present disclosure. It istherefore intended that the present disclosure not be limited to theexact forms and details described and illustrated, but fall within thescope of the appended claims.

What is claimed is:
 1. An interconnect structure for a circuit board comprising: a component circuit board containing a plurality of electrical components; a wafer connector assembly including a plurality of interconnect circuit boards that are in electrical connection with the components circuit board through a plurality of rows of solder joints, the plurality of interconnect circuit boards having a connection end including at least one contact and a backside end opposite the connection end; and an adhesive adhering to and structurally reinforcing at least a first row of solder joints from said plurality of rows of solder joints that is proximate to the connection end of the plurality of interconnect circuit boards of the wafer connector assembly, wherein at least a middle row of solder joints from said plurality of rows of solder joints that is between the connection end and the backside end of the interconnect circuit boards is free of adhesive and wherein the adhesive structurally reinforcing the solder joints relieves strain induced on said solder joints when engaging the wafer connector assembly to the header site of a mid plane board of a computing system chassis.
 2. The interconnect structure of claim 1, wherein the component circuit board is a printed circuit board.
 3. The interconnect structure of claim 2, wherein components of said component circuit board including memory, resistors, capacitors, light emitting diodes (LEDs), transistors, inductors, integrated circuits, and combinations thereof.
 4. The interconnect structure of claim 1, wherein the interconnect circuit boards are printed circuit boards including circuits for providing electrical communication from the at least one contact to solder joints of said plurality of solder joints that are connected to the printed circuit boards.
 5. The interconnect structure of claim 1, wherein the adhesive comprises an epoxy based composition.
 6. The interconnect structure of claim 1, wherein the adhesive is heated.
 7. An interconnect system comprising: a header site for integration with a computing system chassis; and a component circuit board for reversible electrical connection to the header connection site of the computing system chassis through a wafer connector assembly that is solder joint connected to the component circuit board, the wafer connector assembly including a plurality of interconnect circuit boards that are in electrical connection with the components circuit board through a plurality of rows of solder joints, wherein an adhesive is present encapsulating at least a row of solder joints to structurally reinforce the plurality of rows of solder joints and is absent from at least a middle row of solder joints, wherein the adhesive comprises diglycidyl ether of bisphenol F or diglycidyl ether of bisphenol A.
 8. The interconnect structure of claim 7, wherein the component circuit board is a printed circuit board.
 9. The interconnect structure of claim 7, wherein components of said component circuit board including memory, resistors, capacitors, light emitting diodes (LEDs), transistors, inductors, integrated circuits, and combinations thereof.
 10. The interconnect structure of claim 7, wherein the adhesive structurally reinforcing the solder joints relieves strain induced on said solder joints when engaging the wafer connector assembly to the header site of a mid plane board of a computing system chassis.
 11. The interconnect structure of claim 7, wherein the interconnect circuit boards are printed circuit boards including circuits for providing electrical communication from the at least one contact to solder joints of said plurality of solder joints that are connected to the printed circuit boards.
 12. The interconnect structure of claim 7, wherein the adhesive is heated.
 13. An interconnect structure for a circuit board comprising: a component circuit board containing a plurality of electrical components; a wafer connector assembly including a plurality of interconnect circuit boards that are in electrical connection with the components circuit board through a plurality of rows of solder joints, the plurality of interconnect circuit boards having a connection end including at least one contact and a backside end opposite the connection end; and an adhesive adhering to and structurally reinforcing at least a first row of solder joints from said plurality of rows of solder joints that is proximate to the connection end of the plurality of interconnect circuit boards of the wafer connector assembly, wherein at least a middle row of solder joints from said plurality of rows of solder joints that is between the connection end and the backside end of the interconnect circuit boards is free of adhesive.
 14. The interconnect structure of claim 13, wherein the component circuit board is a printed circuit board.
 15. The interconnect structure of claim 14, wherein components of said component circuit board including memory, resistors, capacitors, light emitting diodes (LEDs), transistors, inductors, integrated circuits, and combinations thereof.
 16. The interconnect structure of claim 13, wherein the interconnect circuit boards are printed circuit boards including circuits for providing electrical communication from the at least one contact to solder joints of said plurality of solder joints that are connected to the printed circuit boards.
 17. The interconnect structure of claim 13, wherein the adhesive comprises an epoxy based composition.
 18. The interconnect structure of claim 13, wherein the adhesive is heated.
 19. The interconnect structure of claim 13, wherein the adhesive comprises diglycidyl ether of bisphenol F.
 20. The interconnect structure of claim 13, wherein the adhesive comprises diglycidyl ether of bisphenol A. 